Method of preparing nonpyrogenic medical absorbent wadding



Patented Aug; 8, 1950' UNITED; TATE METHOD OF PREPARING. .NONPYROGENIC MEDICAL ABSORBENT WADDING Claude Chavanon, Itoanne, France N Drawing, Application July 24, 1947, SerialNo.

I 763,449. Infranoe September 18, 1942 I Section 1, Public-Law 690, A'ugu'st 8,1946

' Patent-expires September 18, 1962 3 c aims.

invention relates to medical absorbent wadding. More particularly, it relates to a method of producing medical absorbent wadding from viscose rayon waste and to thevproduct resulting vtherefrom. i

Considerable viscose rayon waste is obtainedin the production of viscose yarn and viscose staple.

into fabrics. During the conversion, of the fabrics .into various articles wherein the fabric is out, there is also considerable waste in the form x ventio'nwill become apparent by reference'to theof cuttings. The waste resulting from operations,

utilizing twisted yarnsor fabrics is, known'a's. "hard waste, and thevwaste obtained in opera-..

tions wherein the .viscose rayon is in the form of untwisted filament or staple fiber known soft waste.

Viscose rayon is produced by extruding a cellulose xanthate solution into a coagulating 1 andregenerating bath whereby some of thersulfur' formed duringthe conversion of the .xanthate into regenerated cellulose is retained in and on the filaments. In the usual processes, theyarn is subjected to a desulfuring operation 'and,

preferably also, a bleaching operation.

medical absorbent wadding from viscose rayonl Another object of this invention is to provide medical absorbent wedding made of viscose rayon I waste and which wadding will not inducefever when used on open wounds.

An additional objectQof thisinvention provide medical absorbent wadding m d of viscose rayon Waste and which will not disintegrate into a powder during storage;

A further object of this invention is to provide; a'method of preparing medical absorbentwa dding consisting essentially of waste viscose rayon, v

350 offlg with' the following solution:

Other and additional objects" of the invention will become apparent hereinafter.

The objects of the invention are accomplished,

in general, by subjecting rayon waste to'aseries of treatments wherein any pyrogenic-substance,

and particularly sulfur," is removed to an extent that the product is no longer pyrogenic,' and thereafter converting th treated fibers into a wadding'whichis neutral and capable of being Likewise, considerable waste is obtained during the production of twisted yarns either. from. continuous filaments or staple rayon.

Waste is also obtained during the weaving or knitting of viscose rayon yarns (either the continuous filament type or spun stapl rayon type) sterilized. The waste, andespecially if itishard waste, is subjected to a picking operation wherein thefibersare opened up without any substantial breaking up of the fibers.

45 fibers are. subjected-to desulfurizing and bleaching operations to remove the sulfur. Sinc the waste is generallyin a dry state, prior to the desulfurizing operation the waste is preferably subjected to a boil-off wherein the fibers are 10 caused. to vas'sumea gel state so that the sub-- sequent treatments can be more effectively car ried' 'out. All Ofthe chemical operations are carriedout under conditions and with concen- The opened up "tration'sof the reagents as will not deleteriously degrade the fibers.

,Thedetails and manner of practicing the inbodiment ofthe invention and that the scopeof the invention is not restricted thereto:

"Example 7 v Dry rayon waste is subjected to a picking operation whereinthe fibers are opened up withoutbreaking thereof, andthe picked raw waste is subjected to the following treatments; the :5 quantities and concentrations hereinafter set forth being for "each 100 kilograms of the picked raw waste: v I V e (a) first boil-ofii- -The dry picked fibers are introduced inra closed kier and subjected .to a boil-oif for 3 hours, at a temperature of 95 C.

andunder a pressure of 2.5 kgs. per square. centimeter, with the following solution which is circulated by means of a centrifugal pump through a system including the'kier:

Causticsoda (92%-95% pure sodium 40 hydroxide) kilogram's 15 Sodium carbonate (Solvay) do -10 1 C astile"soap-("72%) s do At,.the endof this bOil-Ofi, the material. isrinsed ,45 with water at a temperature 0f C. V

(1 Second boiZ-o,fi.- -The material resulting-f from step {(a)..is'subjectedtoa second boil-011% f "-forzhours (under the same conditions of tem-, perature and pressure as those of the first boil-,

v H At' theend ofthis econd boil-oil, the material is rinsed with water at a temperature of' 50 C.

(c) Desulfurization.1n a kier employed for the boil-off operations as above disclosed, the boiled-01f fibers are subjected to a circulating solution ,at a temperature of 60-80 C. and consisting of 2500 ls. of water and 15 kgs. of sodium sulfide for 30 to 35 minutes, the circulation being effected by a centrifugal pump. At the end of the treatment, the solution is separated from.

the fibers, which are then rinsed with slightly acidulated water at a temperature of 50 C.

(d) BZeaching.The material is removed to an open kettle where, after it has been rinsed first with water at room temperature, it is treated with a circulating bath consisting of a 3 B. aqueous solution of sodium hypochlorite for a period of about 3 hours, whereby the material is uniformly impregnated, after which the solution is removed and the material is rinsed with water for minutes. 3

(e) DechZorinatz'on.The material resulting from step (d) is treated with a circulating solution consisting of 3000 ls. of water and 12 ls. of commercial hydrochloric acid for 35 to 40 minutes, after which the solution is removed and the material rinsed with cold water.

(1) Soaking.The material is next put into a vat equipped with stirring forks and valve-conthere is added a solution consisting of 2 kgs. of sodium sulfite per 1000 ls. of water, and the material is permitted to soak therein for 15 minutes, after which the outlet valves are opened and the solution drained. Then the water valves are opened and the material washed 2.0 minutes in continuously running water.

(g) Wash.The vat containing the material from step (f) is filled with water and the stirring apparatus is operated, whereby the material is stirred in all directions in continuously renewed water until the wash water is free of sulfur and compounds containing the same. This treatment takes about 1 hour.

(h) The product is then treated with a bluing, such as ,methylene blue, to enhance its whiteness. I

The product is then appropriately dried, as by' centrifuging, and the dried material is.con-, verted into an unwoven lap of appropriate size, as by carding. or rolls of appropriate size and packaged.

The method of this invention is equally applicable to the treatment of hard or soft viscose rayon waste or, indeed, to dry viscose rayon yarn or fibers as normally produced. When hard viscose rayon waste is utilized, the latter is subjected to thepicking operation set forth in the specific example. The picking operation need not be utilized with soft viscose rayonwaste, but even with such waste better results are obtained when the picking operation is utilized therewith.

The invention is notrestricted to the specific concentrations, temperature and pressure con ditions set forth in the example. the temperature and pressure conditions as well as the concentration of the solutions employed in the respective steps are such as not to deleteri- The lap can be formed into sheets- In general,

carried out under room temperature, and accordingly this temperature is preferred therefor.

As shown by the example, the boil-off is preferably performed in two operations, the second boil-off being carried out with a solution in which the alkali content is less than that of the first boil-off. It has been found that carrying out the boil-off in two stages, as set forth in the example, is more effective than carrying out the boil-off in a single operation. When the boiloff is carried out in a single step, the fibers are attacked, with the result that a product which is not as satisfactory as that obtained with a double boil-off results.

Instead of carrying out the boil-off and desulfuring treatment separately, as disclosed in the example, the boil-off and the desulfuring treatment can be combined. A suitable solution for carrying out the combined operation of boiloff and desulfuring comprises an aqueous solution containing 5 grams per liter of anhydrous sodium hydroxide and from 0.2% to 0.5% sodium Sucha solution is employed at 95 C. If "desired, in place of the sodium sulfide, trisodium phosphate in a concentration of 1 gram per liter can be used. Optionally, a wetting v agent, such as a sulfate of a higher alcohol, can trolled inlets and outlets. When this vat is filled,

also be incorporated in the baths which simultaneously boil-off and desulfur.

The product of the method can be rendered cracky by soaking it in an aqueous solution containing 1 gram of lactic acid per liter.

In carrying out the process, when the fibers are to be separated from. the solution this can be obtained in various manners and preferably by any appropriate bluing dye which has no pyrogenic reaction.

The product. of this invention is absorbent wadding which can 'besterilized and, either in the sterilized or unsterilized condition, will not disintegrate even when kept for prolonged pcriods of time. Due to the chemical operations to which the rayon waste has been subjected, the product will not induce any pyrogenic reaction when used as a medical absorbent wadding on open wounds in place of or as a substitute for medical absorbent. cotton.

Since it is obvious that many changes and modifications can be made in the above-described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited thereto except as set forth in the appended claims.

I claim: I

1. Amethod of preparing non-pyrogenic medical absorbent wadding which comprises picking open the fibers of viscose rayon waste, subjecting the picked fibers to a two-stage alkaline boil-01f in caustic soda solution, the first stage contain- --.ing ahigher concentration of caustic soda than the second stage, desulfuring said fibers by treatment with asodium sulphide solution, bleaching said desulfured rayon fibers, Washing the resulting fibers while continuously stirringin all direc tions until the wash water is free of sulfur and sulfur-containing compounds, drying said. fibers,

and converting them to an unwoven lap.

2. A method of preparing non-pyrogenic medical absorbent wadding which comprises picking open the fibers of viscose rayon waste, subjecting the second stage, desulfuring said fibers by treatment in a sodium sulphide solution, bleaching said desulfured rayon fibers by treatment with sodium hypochlorite, soaking said fibers in a dilute aqueous solution of sodium sulfite, washing the resulting fibers while continuously stirring in all directions until the wash water is free of sulfur and sulfur-containing compounds, drying said fibers, and converting them to an unwoven lap.

3. A method of preparing non-pyrogenic medical absorbent wadding which comprises picking dry viscose rayon, boiling 011? the dry opened up viscose rayon fibers in a two-stage boiling-off operation, the first stage comprising subjecting the fibers for 3 hours at a temperature not in excess of 95 C. with the following solution:

Water 1iters 3500 Caustic soda (92%-95% pure sodium hydroxide) kilograms 15 Sodium carbonate (Solvay) do Castile soap (72%) -1d0 5 the second stage of the boil-off being performed under the same conditions as the first boil-off except that it is performed for 2 hours with the following solution Water liters 3500 Caustic soda (92%-95% pure sodium hydroxide) "kilograms" ;12

Sodium carbonate (Solvay) do 10 Castile soap (72%) do 6 subjecting the boiled-off fibers to a solution at -80 C. and consisting of an aqueous solution containing 0.6% sodium sulfide, bleaching the desulfured fibers with a 3 B. aqueous solution of sodium hypochlorite, subjecting the bleached material to an anti-chlor, soaking the resulting material in an aqueous solution containing 0.2% sodium sulfite, removing said sodium sulfite solution, washing the resulting material while being continuously stirred in all directions with continuously renewed material until the wash water is free of sulfur and compounds containing the same, drying the material, and converting it into an unwoven lap.

CLAUDE CHAVANON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,404,535 Luft Jan. 24, 1922 1,786,781 Shoemaker Dec, 30, 1930 1,872,076 Dreyfus Aug. 16, 1932 1,906,983 Lockhart May 2, 1933 1,915,072 Richter June 20, 1933 

1. A METHOD OF PREPARING NON-PYROGENIC MEDICAL ABSORBENT WADDING WHICH COMPRISES PICKING OPEN THE FIBERS OF VISCOSE RAYON WASTE, SUBJECTING THE PICKED FIBERS OF VISCOSE RAYON WASTE, SUBJECTING THE PICKED FIBERS TO A TWO-STAGE ALKALINE BOIL-OFF IN CAUSTIC SODA SOLUTION, THE FIRST STAGE CONTAINING A HIGHER CONCENTRATION OF CAUSTIC SODA THAN THE SECOND STAGE, DESULFURING SAID FIBERS BY TREATMENT WITH A SODIUM SULPHIDE SOLUTION, BLEACHING SAID DESULFURED RAYON FIBERS, WASHING THE RESULTING FIBERS WHILE CONTINUOUSLY STIRRING IN ALL DIRECTIONS UNTIL THE WASH WATER IS FREE OF SULFUR AND SULFUR-CONTAINING COMPOUNDS, DRYING SAID FIBERS, AND CONVERTING THEM TO AN UNWOVEN LAP. 